1. Field of the Invention
The present invention relates to rail car braking systems and, more particularly, to an automatic parking brake that may be used with body mounted brake cylinders.
2. Description of the Related Art
Most rail vehicles have a manually-operated parking brake that applies the wheel brakes. Unfortunately, this requires that an operator manually apply the brake on each rail car in a train. As a result, an automatic parking brake, such as that disclosed in U.S. Pat. No. 7,163,090, has been developed that will retain the braking system of any rail car equipped with the brake in the brakes applied position if brake pipe pressure is removed from a locking mechanism position about the shaft of the brake cylinder. Body mount brake cylinders are typically constructed with a hollow rod affixed to the piston and apply the brake force to the brake rigging by means of a push rod inside the hollow rod. This arrangement accommodates angular misalignment of the push rod as the connected brake lever operates through an arc, and decouples the manual hand brake from the body mount cylinder when the cylinder is released and the hand brake applies. In this condition, the hand brake acts on the same brake rigging as the body mount brake cylinder. In the hand brake applied position, the rigging pulls the body mount brake push rod independent of the brake piston, allowing the brake piston to remain in the released position, and decouples the influence of the body mount brake cylinder return spring from the hand brake application. Accordingly, there is a need for an automatic parking brake that can be used with body mounted braking systems while still using a hollow rod, or the same functionality as a hollow rod, so that the piston rod can still accommodates angular misalignment as the connected brake lever operates through an arc.